Answer:
255.34 J
Explanation:
Given,
Weight of disk = 805 N
radius = 1.47 m
Force applied by the child = 49 N
time = 2.95 s
KE = ?
mass of the disk

Moment of inertia of the disk


Torque on the child

Angular acceleration

So, angular speed at t = 2.95 s

Now, KE of the merry go round

Hence, the Kinetic energy of the merry go round = 255.34 J
I’m pretty sure it’s B
B: If an object has mass, it has gravity.
Answer:
Explanation:
We shall apply Doppler's effect to solve the problem .
Formula for apparent frequency for a source of sound approaching an observer is as follows .
f₁ = f₀ V / (V - v )
where f₁ and f₀ are apparent and real frequency of source , V and v is velocity of sound and velocity of approaching source respectively .
Putting the given values and knowing that speed of sound is 340 m /s
f₁ =346x 340 / (340 - 39.6 )
f₁ = 391.6 Hz
In case of receding train , the formula is
f₂ = f₀ V / (V + v )
Putting the values
f₂ = 346x 340 / (340 + 39.6 )
= 309.9 Hz
Change in frequency = 391.6 - 309.9
= 81.7 Hz .
Answer:
is a reflection.
The image is real light rays actually focus at the image location). As the object moves towards the mirror the image location moves further away from the mirror and the image size grows (but the image is still inverted). When the object is that the focal point, the image is at infinity.
Explanation:
If the tension in the rope is 160 n, - 43200 J work doen by the rope on the skier during a forward displacement of 270 m.
Given,
Tension force in the rope is (T) = 160 N
Displacement of the skier (S) = 270 m
The displacement takes place in forward direction while the direction of the tension in the rope is opposite to it.
Therefore, work done by the rope on the skier is,

⇒
Hence work done by the rope is - 43200 J.
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